Various methods for classifying objects in a field of view are known in the art. Typically, a sensor system of some kind, such as a CCD detector and its related optics or a night-vision system, will sweep through a wide Field Of View (FOV) while continuously scanning it. An individual Field Of Regard (FOR) will be scanned once per rotation, or sweep, where an individual FOR is the scene which is detectable by the sensor system at a given instant. The result of scanning an individual FOR, at a given time, produces positional measurements regarding the objects in the FOR.
Any stationary object in an individual FOR can easily be classified since it will appear in the same location in each scan of that FOR. Moving objects, however, are more difficult to classify since their locations in the FOR change between scans of the FOR. In addition, when there are a number of moving objects in the FOR, it is a non-trivial problem to define which of the measurements belong to one moving object and which belong to another. This ambiguity arises because the time between scans of an FOR, known as the revisit time, is typically long compared to the rate of movement of the objects.
One solution is to increase the sweep rate in order to decrease the revisit time. Unfortunately, a fast sweep rate typically produces low signal to noise ratios (SNR) and can smear the measurements. This produces an unacceptably high level of measurements which do not belong to a true moving object; such measurements are known as false measurements, or false alarms. Additionally, for some of the scans of the individual FOR, there will be no measurement of the moving object, even though the object was present, due to the fast sweep rate. This causes a reduction of the probability of detection of moving objects.
Classification and tracking of multiple targets is known in the art as Multiple Target Tracking (MTT) and it has a number of applications, both military and non-military. The military applications include sophisticated weapon delivery systems and satellite surveilance and the non-military applications include air-traffic control. MTT is described, for example, in the book Multiple-Target Tracking with Radar Applications by Samuel S. Blackman, published by Artech House, Inc. Dedham, Ma., 1986.